Protective alarm system for metal-enclosed apparatus



Se t. 21, 1965 J. P. GERVASI ETAL 3,203,051

PROTECTIVE ALARM SYSTEM FOR METAL-ENCLOSED APPARATUS Filed Feb. 15, 1963 2 Sheets-Sheet 1 Ill/II III! III!!! III!!! III!!! B T INVENTORS Joseph Peter Gervosi, BY Nathan Robinson ATTORNEYS l 1965 J. P. GERVASI ETAL 3,208,061

PROTECTIVE ALARM SYSTEM FOR METAL-ENCLOSED APPARATUS 2 Sheets-Sheet 2 Filed Feb. 15, 1965 I E 651 l R. F. FREQUENCY 1 ETT2A L o5=|EE 2? 4 FROM 1 ALARM W REMOTE INDICATORS 1 RECEIVERS 1 POWER I 1 l PPLY INVENTORS J Joseph Perer Gervosi,

71 Nathan Robinson United States Patent 3,208,061 PROTECTIVE ALARM SYSTEM FOR METAL-ENCLUSED APPARATUS Joseph Peter Gervasi, 2620 University Ave, and Nathan Robinson, 2335 W. Lawn Ave, both of Madison, Wis. Filed Feb. 13, 1963, 'Ser. No. 258,340 7 Claims. (Cl. 340-224) This invention relates to a protecting system, and more particularly to an indicating or alarm system for protecting remote devices, such as parking meters, from unauthorized tampering.

A substantial amount of publicity has recently been given to the problems of various municipalities in protecting parking meter apparatus from destruction and from theft of the coins collected in such apparatus. Vandals and thieves have gone so far as to remove entire parking meters in some cases and in other cases have in some way attempted to gain access to the coin boxes in such meters,

either through obtaining keys that will fit the metal locks,

or forcing the locked doors open.

Various solutions to these problems have been suggested, such as making parking meters of sturdier construction so as to increase the difficulty of obtaining access to the coin boxes thereof. Of course this solution will not solve the problem that exists of a thief removing an entire parking meter and having a key constructed that will fit the lock thereof so that he can readily obtain access to the coin boxes in other parking meters. When this type of problem has existed in the past, it has often been necessary to change the locks on the parking meters, at great expense and inconvenience to the municipality.

Another previously-suggested solution is the installation of alarm systems which will detect any tampering with the meters. One such alarm system employs wire circuits connected from each of the meters to a central alarm station, by electric wires. This of course involves the necessity of concealing the wires in some fashion, if the alarm system is not to be subject to disconnection by an enterprising thief. In the case of new installations where parking meters are installed on a new parking ramp as it is constructed, it is fairly simple to bury the wires in the concrete forming the ramp. However, where an existing parking meter installation is to be protected, the burial of such wires in the adjacent concrete is obviously expensive and therefore impractical.

Another prior suggestion for protection of parking meters by an alarm system is illustrated in the patent to Miller, No. 2,937,269, issued May 17, 1960. In this system each parking meter has a radio transmitter installed in the standard which supports the meter head; and if a manual switch in the meter is not cut oif by an authorized person, before tampering with the coin box is attempted, another switch is closed by opening of the coin box door to actuate the transmitter. The system further includes a remote receiver responsive to the radio signal from the transmitter, to furnish an appropriate alarm. One problem with the Miller-type of system is that the transmitter is quite large and is difficult and therefore expensive to mount in the parking meter. Further, in the case of meters having very short, hollow columns, such as those supported by L-shaped arms extending from a building, the vertical lengths of the columns are too short to permit mounting of the transmitter therein.

An even more important problem met in construction of the type of system suggested by Miller is that it is quite diiiicult to obtain a substantial amount of radiated power 3,233,061 Patented Sept. 21, 1965 from a radio transmitter which is mounted in a metal structure, such as the conventional parking meter. Miller suggests solution of this problem by use of a portion of the metal column as a radiator, that portion being connected to the transmitter and therefore functioning as an antenna. We have found it very difficult to provide a signal of sufiicient strength at a location substantially displaced from the parking meter, with a transmitter of reasonable size, when the parking meter column is to be used as the radiator.

A further problem with the system suggested by Miller is that it is relatively easy to disable the alarm system, as by use of a bar or shorting wire which may be applied to the meter column to ground it. Also, the system in an entire area may be rendered useless by a radio transmitter of the same frequency as the alarm transmitter.

It is a prime object of this invention to provide a simple radio alarm system for parking meters, to protect such meters against unauthorized tampering therewith. It is a further object of the invention to provide effective radio transmitters for such a system which are small, inexpensive, and easily installed in the meters. Another object of the invention is to make it extremely difiioult for anyone to render the alarm system ineffective, even if that person has knowledge of the design of the alarm system.

A further object of the invention is to obtain a radiated signal of detectable power at a location a reasonable distance from the protected meter without the use of a high power transmitter, and wihout substantial modification to the parking meter itself.

The above and other objects of the invention are realized through the use of a small, relatively low power radio transmitter which is mounted preferably within the meter head and which supplies power to an antenna effective to radiate that power to a substantial distance away from the transmitter. That antenna is mounted opposite the window of the parking meter which permits observation of the unexpired time for which the meter may be used. Preferably, the antenna includes the metal meter dial face, which, being mounted opposite the glass window, is not completely shielded by the metal cover of the meter and is therefore effective to radiate the radio signal a substantial distance from the meter. The transmitter of the invention further preferably includes a modulating frequency oscillator connected to the radio frequency oscillator to modulate the output thereof, and a radio receiver responsive only when the modulating frequency is received, with the result that it is much more difficult for anyone to render the alarm system ineffective.

The invention will now be more fully described in conjunction with drawings showing a preferred embodiment thereof. It will be understood, however, that the invention is not limited to the preferred embodiment of the drawings, and in fact is not limited to use of the system in connection with parking meters, but rather is only limited by the scope of the appended claims.

In the drawings,

FIG. 1 is a partially perspective and partially elevational view of a series of parking meters protected by the alarm system of the invention;

FIG. 2 is a detailed view of a portion of the apparatus of the invention, showing the use of the metal meter dial as the antenna for the transmitter;

FIG. 3 is a schematic view of the radio transmitter of the invention; and,

FIG. 4 is a block diagram showing of the receiver and alarm system.

Referring first to FIG. 1, the protective alarm system of the invention may be designed to protect a plurality of spaced parking meters 16. Each of these meters may be of conventional design and in fact may be of many different designs well known in the art. Such meters customarily include a column or standard 11 which supports a meter head 12. Both the head and the column are customarily of metal, so that the apparatus inside the parking meter is electrically shielded by the metal cover. However, the meter head also includes an upper compartment 13 which contains the meter itself (not shown), a metal dial face 14, and a pointer 15 which moves along the dial face to indicate the unexpired time available for parking adjacent the meter.

Access to the meter, as for repair and replacement of parts thereof, is obtained through a hinged front door 16 which is held in position by a key-operated lock 17 intended to prevent any unauthorized person from obtaining access to the meter.

The meter head also includes a lower hinged door 20 which is held closed by a key-operated lock 21. The lower compartment contains a coin box 22 into which fall coins inserted through the slot 23 in the upper portion of the head.

Anyone desiring to tamper with the parking meter will normally be attempting to obtain access to the coin box 22 and will therefore attempt to open the lower door 20.

The apparatus of the invention includes a radio transmitter generally shown at 25 and mounted within the upper compartment of the parking meter head 12. It further includes a power supply operative when connected to the radio transmitter to cause actuation thereof, such power supply preferably comprising a battery 26 which is mounted adjacent the transmitter in the upper compartment of the meter head. The apparatus of the invention further includes a switch 27 mounted on the door 20 and responsive to movement of that door to complete the connection between the battery 26 and the transmitter 25 to cause actuation of the transmitter.

Referring now to FIG. 3, the radio transmitter 25 may be of any suitable well-known type which includes a radio frequency oscillator 36 and a modulator 31. It is preferred that such transmitter employ transistors, rather than vacuum tubes, because of the small size and low power drain of such electronic devices. The modulator shown includes a PNP transistor 32 having its emitter connected to ground (which may be the metal case of the parking meter) through a bias resistor 33. The base of the transistor 32 is appropriately biased by a voltage divider including resistors 34 and 35 which are connected across the power supply battery 26. The collector of transistor 32 is connected to the shunt combination of a capacitor 36 and a tapped inductor 37, which form the tank circuit for the modulating frequency oscillator. The other end of the tank circuit is connected through a feedback capacitor 38 to the base of transistor 32, while the tap is connected through mercury switch 27 to the negative terminal of the battery 26.

The radio frequency oscillator 30 includes a PNP transistor 40 which has its emitter connected to ground through a bias resistor 41 which is appropriately bypassed by a capacitor 42. The base of transistor 40 is appropriately biased by connection to a voltage divider comprising resistors 43 and 44 connected across the power supply battery 26. The resistor 44 is shunted by a by-pass capacitor 45. The collector of transistor 40 is connected to a radio frequency tank circuit comprising a tapped inductor 46 and a pair of shunt capacitors 47 and 48, the capacitor 48 being variable to tune the tank circuit. One of the taps on the coil 46 is connected through the frequency-determining crystal 49 to the base of transistor 40 to provide feedback at the frequency characteristic of that crystal, so that the oscillator 30 may function to supply high frequency power.

The junction between the crystal 49 and the tapped inductor 46 is connected through a coupling coil 50 to the metal meter face 14 of the parking meter. Such faces are normally connected at both ends to the meter case, but the terminal 51 to which the coil 50 is connected is preferably insulated from the case, in order that the meter dial face may act as an antenna in the operation of this invention. The opposite end 52 of the dial may be left connected to the meter head or case.

In order that the voltage output of the modulator 31 may modulate the radio frequency voltage from oscillator 30, the junction between the modulator tank and the collector of transistor 32 is connected to the terminal of the radio frequency oscillator tank remote from the collector of transistor 40. This connection is by-passed to ground for radio frequencies by capacitor 55.

In operation of the transmitter of FIG. 3, when the switch 27 is closed by movement of the lower access door 20 from its closed to its open position, the battery power supply 26 is connected to the transistors 32 and 40 to furnish operating biases therefor. The radio frequency oscillator 30 then functions to furnish a radio frequency voltage across the tank circuit inductor 46, and that voltage is modulated by the output of modulator 31. As shown in FIG. 2, the tapped coil 46 may consists of a number of separate coils mounted on an insulated form 56 and connected in series. The coil 50 is preferably inductively related to the coil 46 by being wound around the coil form 56 in an axial direction.

As a result of these connections, the radio frequency voltage, as modulated by the modulator 31 is supplied to the transmitting antenna formed by the meter dial face 14, and a modulated radio signal is radiated out of the meter casing through the Window in front of that dial face.

Referring again to FIG. 1, signals from any one of a plurality of such transmitters, mounted in different parking meters, may be detected at a suitable conventional radio receiver 60 connected to an antenna 61. This antenna may be strung along the area in which the protected meters are located, as from poles 62 and 63, with the antenna 61 being close enough to each one of the meters so as to provide a radio frequency voltage of detectable power at the input of the receiver 60. Of course the antenna may be strung from existing power or telephone poles, may be supported by building adjacent the parking meters, or may be strung along the ground or pavement in the area of such meters.

As indicated, the receiver may be of any conventional well-known design which is constructed so as to detect the modulation voltage associated with the radio frequency signal on the antenna 61. For instance, referring to FIG. 4, the receiver 60 may include a radio frequency amplifier 65 receiving its input from the receiving antenna 61 and supplying its output to a frequency converter 66. The intermediate frequency output of the converter 66 may then be amplified by an intermediate frequency amplifier 67 before being supplied to a demodulator 68. The demodulator 68 may be designed to furnish an operating voltage for the coil of a relay 69 mounted on or in the receiver 60 and which has a pair of normally-open contacts 70.

The demodulator 68 may be designed to supply an operating voltage for relay 69 to cause closure of its contacts only when a radio signal of the frequency of oscillator 30 modulated by a signal of the frequency of modulating oscillator 31 is supplied to the antenna 61, in which case maximum protection against jamming of the system will be achieved. Alternatively, the demodulator 68 may be frequency-insensitive, so that a modulating signal of any frequency will be detected. In such case somewhat less protection against jamming will be achieved, yet anyone desiring to jam the system will still have to know both the frequency of the oscillator 30 and the fact that the radio signal is modulated.

The contacts 70 of relay 69 may be connected to any appropriate alarm system which may be located at some remote location, such as a police central oflice or precinct station, for instance, over telephone lines. Closure of the relay contacts may be employed to complete a circuit including an appropriate power supply 71 and one of a set of appropriate indicator 72 such as a bell and/or a light.

It will be evident that a number of such alarm systems, each including one receiver and a plurality of transmitters mounted within parking meters, might be employed to protect the parking meters of an entire city. The central alarm system might then include a separate indicator for each of the receivers, so that the location of the parking meter being tampered with could be apparent to a radio dispatcher who might then direct a police car to that area to apprehend the person tampering with the meter.

From the above description it will be apparent that the details of the receiver and alarm system are not at all themselves important to the present invention. All that is necessary is that a suitable receiver which will respond to the modulated signal from a transmitter mounted in a remote parking meter he provided, and that such receiver be operable to furnish an indication of tampering when the transmitter in the parking meter is actuated. It is, however, very important to the present invention that the transmitting antenna be mounted adjacent an opening in the metal cover of the parking meter, such as that opening furnished by the glass opposite the meter dial. While an antenna separate from any part of the normal parking meter could be employed in this dial area, it is preferable both from the standpoint of expense and security that the meter dial itself be used as at least a part of the transmitting antenna.

It is also of importance to the invention that the transmitter and its power supply be small enough so that they can be readily located within the upper meter compartment of the parking meter, since that compartment is one which a thief would normally not interfere with since he would know that the coins are in the lower coin box compartment. Nevertheless, if it is desired to protect against the possibility of a thief obtaining access to the upper compartment to disable the transmitter before attempting to gain access to the lower compartment, the upper compartment may also be provided with a switch mounted on the upper door 16 and responsive to opening thereof to actuate the transmitter. In such case, the switch may also be a mercury switch of the same type as that shown at 27 and may be connected across that switch to furnish power to the transmitter when the upper door is moved.

While mercury switches have been specifically referred to hereinabove, it will be apparent that the particularly type of switch is not critical to the invention, so long as a normally-open switch which is sensitive to movement thereof to furnish a closure between the terminals is supplied.

Finally, an important feature of the invention is the use of a modulated frequency radio signal since the likelihood of anyone knowing both the frequency of the radio signal and the frequency of modulation, so as to be able to jam all the receivers in an area, is small.

It will be evident that many minor modifications could be made in the details of the apparatus shown as the pre ferred embodiment of the invention. Further, as indicated above, though this invention is primarily intended for use in protecting parking meters, it will be evident that it might be adapted to other purposes such as protection of coin-operated telephones. Accordingly, the invention is not to be considered limited to the details shown in the drawings, but rather only by the scope of the appended claims.

We claimz' v 1. Apparatus for protecting at least one coin-operated parking meter from unauthorized tampering therewith, said parking meter being of metal but having a glass window opposite a metal meter dial and having a coin box accessible for removal of coins thereof, comprising:

a radio frequency transmitter mounted within said parking meter so as to be generally shielded by the metal thereof, said transmitter being operable when actuated to supply radio frequency voltage at its out- P transmitting antenna means including said metal meter dial connected to the output of said transmitter to radiate a radio signal of detctable power to a loca tion a substantial distance from the parking meter when the transmitter is actuated,

means connected to said transmitter and responsive to tampering with said coin box to actuate the transmitter,

and means including a radio receiver having a receiving antenna positioned at said location and operable in response to receipt of said radio signal by said receiving antenna to supply an indication of tampering with the parking meter.

2. The apparatus of claim 1 in which said parking meter includes an access door movable from a closed to an open position to expose the coin box,

and said means connected to said transmitter includes a switch mounted on said door and responsive to movement thereof to actuate the transmitter.

3. The apparatus of claim 1 in which said parking meter includes an upper compartment containing the meter and the dial and a lower compartment containing the coin box, said transmitter being mounted in said upper compartment.

4. The apparatus of claim 1 in which said transmitter includes a radio frequency oscillator and a lower modulating frequency oscillator connected to said radio frequency oscillator to modulate the output thereof,

said receiver being operable to supply an indication only when the modulating frequency is detected thereby.

5. Apparatus for protecting at least one coin-operated parking meter from unauthorized tampering therewith, said parking meter including a metal meter head having an upper compartment containing a meter and a metal dial face therefor with a glass window opposite the dial face, and a lower compartment containing a coin box into which coins for operation of the meter fall, each of said compartments being accessible through a separate located door, said protecting apparatus comprising:

a radio frequency transmitter mounted inside said upper compartment,

a power supply for said transmitter also mounted inside the upper compartment,

a normally-open switch mounted on the inside surface of the door of the lower compartment, said switch being operable to furnish a connection between its terminals when said last-mentioned door is opened and being connected between said power supply and said transmitter to cause actuation of the transmitter when said last-mentioned door is opened,

' transmitting antenna means connected to said transmitter to radiate a radio frequency signal to a location remote from the meter when the transmitter is actuated, said antenna means including the metal dial face of said meter, with one end of said dial face insulated from the metal meter head and connected to said transmitter and the other end of said dial face connected to the metal meter head,

and means including a radio receiver having a receiving antenna located at said remote location, said 7 8 means being operable to furnish an indication when 7. The apparatus of claim 5 in which said switch is a a signal is radiated from said transmitting antenna mercury switch responsive to movement thereof.

means. 6. The apparatus of claim 5 in which said transmitter includes a radio frequency oscillator References Cited by the Examiner UNITED STATES PATENTS and a lower modulating frequency oscillator con- 2344 014 3/44 Allison 200*1527 nected to said radio frequency oscillator to modu- 2899674 8/59 Sierer 340 224 late its output when the transmitter is actuated, 21937:269 5 /60 Miner 5 said receiver being operable to supply an indication 3 051 934 3 2 Lesher 34 224 only when the modulating frequency is detected 10 thereby. NEIL C. READ, Primary Examiner. 

1. APPARATUS FOR PROJECTING AT LEAST ONE COIN-OPERATED PARKING METER FROM UNAUTHORIZED TAMPERING THEREWITH, SAID PARKING METER BEING OF METAL NUT HAVING A GLASS WINDOW OPPOSITE A METAL DIAL AND HAVING A COIN BOX AXCESSIBLE FOR REMOVAL OF COINS THEREOF, COMPRISING: A RADIO FREQUENCY TRANSMITTER MOUNTED WITHIN SAID PARKING METER SO AS TO BE GENERALLY SHIELDED BY THE METAL THEREOF, SAID TRANSMITTER BEING OPERABLE WHEN ACTUATED TO SUPPLY RADIO FREQUENCY VOLTAGE AT ITS OUTPUT, TRANSMITTING ANTENNA MEANS INCLUDING SAID METAL METER DIAL CONNECTED TO THE OUPTUT OF SAID TRANSMITTER TO RADIATE A RADIO SIGNAL OF DETCABLE POWER TO A LOCATION A SUBSTANTIAL DISTANCE FROM THE PARKING METER WHEN THE TRANSMITTER IS ACTUATED, MEANS CONNECTED TO SAID TRANSMITTER AND RESPONSIVE TO TAMPERING WITH SAID COIN BOX TO ACTUATE THE TRANSMITTER, AND MEANS INCLUDING A RADIO RECEIVER HAVING A RECEIVING ANTENNA POSITIONED AT SAID LOCATION AND OPERABLE IN RESPONSE TO RECEIPT OF SAID RADIO SIGNAL BY SAID RECEIVING ANTENNA TO SUPPLY AN INDICATION OF TAMPERING WITH THE PARKING METER. 